Thrombosis & Embolism Flashcards
explain thrombus
Thrombus: A thrombus is indeed a stationary blood clot that forms within a blood vessel. It can develop in situ (at the site) and can partially or completely block blood flow. Thrombi can form due to conditions such as atherosclerosis, inflammation, or conditions that affect blood clotting.
Formation of Thrombus: Thrombi can form within the vessel (in situ) due to factors like endothelial damage, blood stasis, and hypercoagulability, which are collectively known as Virchow’s triad.
Location of Thrombus Formation: Thrombi can form in various locations within a blood vessel, including the lumen (the inner space of the vessel), on the vessel wall, or at the site of atherosclerotic plaques. Thrombi can also form in veins, leading to conditions such as deep vein thrombosis (DVT).
Haemorrhage: Haemorrhage refers to the escape of blood from the circulatory system. It can occur externally or internally. External haemorrhage is visible, such as bleeding from a cut or wound. Internal haemorrhage can occur within the body, for example, due to trauma or ruptured blood vessels.
Blood Leaving a Vessel: When blood leaves a vessel, it is indeed called hemorrhage. However, it’s important to note that hemorrhage typically refers to bleeding or blood loss, and it is not synonymous with the formation of a thrombus.
explain the 2 main components of haemostasis
Mechanisms to Stop Bleeding: Hemostasis refers to the physiological processes that the body employs to prevent and control bleeding. This includes vasoconstriction (narrowing of blood vessels), platelet adhesion and aggregation, and the coagulation cascade that leads to the formation of blood clots (thrombus). This aspect of hemostasis is crucial in preventing excessive bleeding after injury.
State of Unimpeded Blood Flow: Hemostasis also refers to the overall state of balanced and controlled blood flow within the blood vessels, where the blood is flowing unimpeded without the formation of abnormal or excessive clots. This aspect involves a delicate balance between pro-coagulant and anticoagulant factors to maintain blood fluidity while preventing unnecessary clotting.
explain hypercoagulability
Hypercoagulability, as you mentioned, refers to a state in which there is an increased tendency for blood clot formation. This can be due to various factors, including genetic predispositions, certain medical conditions, or lifestyle factors. Some common situations or disorders associated with hypercoagulability include:
Inherited or genetic disorders: Conditions such as Factor V Leiden mutation or prothrombin gene mutation can increase the risk of blood clot formation.
Antiphospholipid syndrome: An autoimmune disorder where the immune system mistakenly attacks certain proteins involved in blood clotting, leading to an increased risk of clots.
Cancer: Some types of cancer and certain cancer treatments can contribute to a hypercoagulable state.
Surgery and trauma: Major surgery or trauma can increase the risk of blood clot formation.
Immobility: Prolonged periods of immobility, such as during long flights or bed rest, can contribute to blood clot formation.
Hormonal factors: Certain hormonal conditions, such as pregnancy, use of oral contraceptives, or hormone replacement therapy, can increase the risk of hypercoagulability.
explain exsanguination
Exsanguination refers to the severe loss of blood, often to the point of death or near-death. It can result from trauma, surgical complications, or other medical conditions that lead to significant bleeding. The term is commonly used in the context of severe hemorrhage or blood loss that can be life-threatening if not promptly addressed. Treatment for exsanguination typically involves immediate medical intervention to stop the bleeding and restore blood volume to prevent further complications.
explain terms and definitions
Increased Likelihood of Clot Formation: The term for an increased likelihood of clot formation is “hypercoagulability.”
Blood Passing Through the Walls of a Blood Vessel: The term for blood passing through the walls of a blood vessel is “haemorrhage.”
Fragile Clot Initially Forming at the Site of Injury: The fragile clot initially forming at the site of injury to a blood vessel is called “platelet plug” or “primary hemostatic plug.”
Extreme Flow of Blood Out of the Body: The term for the extreme flow of blood out of the body is “exsanguination.”
Solid Stationary Blood Clot: A solid stationary blood clot is called a “thrombus.”
Process of Forming a Clot: The process of forming a clot is called “coagulation” or “clotting.”
Cessation of Bleeding and Free Flow of Blood Without Clots: The term for the cessation of bleeding and the free flow of blood without clots is “hemostasis.”
explain the terms Rudolf Virchow coined
Thrombosis and Embolism: Virchow made substantial contributions to the understanding of blood clotting and vascular disorders. He is credited with coining the terms “thrombosis” (formation of blood clots within blood vessels) and “embolism” (the obstruction of a blood vessel by an embolus, such as a clot or air bubble).
Cell Theory: Virchow is one of the key figures in the development of the cell theory, which states that all living organisms are composed of cells, and the cell is the basic unit of life. He is particularly known for his statement “omnis cellula e cellula” (every cell originates from another existing cell).
Leukaemia: Virchow contributed to the understanding of blood disorders, including his work on leukemia, a type of cancer that affects the blood and bone marrow.
Chromatin: Virchow made contributions to the study of cellular structure, and the term “chromatin” is related to the material of which the chromosomes of organisms are composed, including DNA and proteins.
Parenchyma: In plant pathology, Virchow contributed to the understanding of plant tissues, and the term “parenchyma” refers to the functional tissue in an organ, as distinguished from supportive or connective tissues.
Spina Bifida: While not directly associated with Virchow, spina bifida is a congenital condition involving incomplete closure of the spinal column. It falls within the broader field of embryology and developmental disorders.
Virchow’s Triad: Virchow’s triad refers to the three factors that contribute to the formation of blood clots: endothelial injury, stasis or turbulence of blood flow, and hypercoagulability. This concept is fundamental to understanding the pathogenesis of thrombosis.
Virchow’s Node: This term refers to a palpable lymph node in the left supraclavicular area, which can be associated with abdominal or thoracic malignancies. It is part of the clinical examination for possible signs of cancer.
explain endothelial injury
Causes of Endothelial Injury:
Trauma or Injury:
Physical trauma to blood vessels, such as injuries or accidents, can lead to endothelial damage.
Venepuncture (puncture of a vein) and cannulation (insertion of a cannula or tube) for medical procedures can also cause endothelial injury.
Pathological Causes:
Cellulitis: Inflammation of the subcutaneous connective tissue.
Thrombophlebitis: Inflammation of a vein associated with the formation of a thrombus.
Atherosclerosis: A condition characterized by the buildup of plaque on the inner walls of arteries, leading to vessel narrowing and potential endothelial damage.
Factors Exacerbating Endothelial Injury:
Endothelial injury can be exacerbated by various factors, including:
Inflammation:
Any inflammatory process in the body can contribute to endothelial injury and promote clot formation.
Infection:
Infections can lead to inflammation and compromise the integrity of the endothelium.
Toxins from Cigarettes:
Smoking introduces toxins into the bloodstream, which can have detrimental effects on the endothelium.
Hypercholesterolemia:
Elevated levels of cholesterol in the blood can contribute to atherosclerosis, leading to endothelial injury.
explain how blood has a laminar flow
In normal, healthy blood vessels, blood flow typically exhibits laminar flow. Laminar flow is a smooth, orderly flow of fluid in which layers of the fluid move parallel to each other, with faster flow at the center of the vessel and slower flow near the vessel walls. This results in a velocity gradient across the diameter of the blood vessel.
In the context of blood flow:
Center of the Vessel (Axis): The fastest flow of blood occurs along the central axis of the blood vessel. This is known as the axial or central stream.
Near the Vessel Walls: The slowest flow occurs near the walls of the vessel. This is often referred to as the boundary layer.
This laminar flow pattern is influenced by factors such as the viscosity of blood, the diameter of the blood vessel, and the velocity of blood. When blood flows smoothly in this laminar fashion, it minimizes turbulence and promotes efficient blood circulation.
However, disruptions to laminar flow, such as turbulence or changes in blood viscosity, can contribute to conditions like atherosclerosis and may increase the risk of blood clot formation.
explain laminar & turbulent blood flow
Laminar flow, characterized by the ordered motion of a fluid in adjacent layers, is a hallmark of healthy blood vessels. In laminar blood flow, the fluid moves smoothly with the fastest flow along the central axis and slower flow near the vessel walls.
On the other hand, turbulent flow describes the irregular motion of a fluid, often forming eddy currents. Unlike laminar flow, turbulent blood flow is associated with several cardiovascular diseases. Disruptions in the normal, smooth flow of blood can contribute to conditions such as atherosclerosis and increase the risk of complications.
explain the typical blood flow in healthy vessels & acknowledging the possibility of turbulence or static conditions
Laminar Flow in Healthy Blood Vessels:
Under normal circumstances, blood in healthy blood vessels exhibits laminar flow.
Laminar flow refers to the smooth, orderly movement of blood in layers, with the fastest flow occurring along the central axis of the vessel and slower flow towards the vessel walls.
Turbulence:
While laminar flow is the norm, certain conditions or factors can disrupt the smooth flow and lead to turbulence.
Turbulent flow involves irregular and chaotic movement of blood, often characterized by swirling or eddy currents.
Turbulence can occur in areas of vessel narrowing (stenosis), at bifurcations, or in the presence of structural abnormalities.
Static Conditions:
Blood may also become static, meaning it comes to a temporary stop or significantly slows down in certain areas.
Static conditions can occur in areas of vessel obstruction, such as blood clots or thrombi, or in regions of very low blood flow.
Are Lines of Zhan more likely if the clot started to form whilst alive or after death?
Lines of Zahn, which are alternating layers of platelets and fibrin, are more likely to be observed in clots that formed while the blood was still flowing, i.e., while the individual was alive. These lines represent the result of the dynamic process of blood clot formation in which there is a mixture of formed elements, including platelets and fibrin, and they are indicative of a thrombus that formed in flowing blood.
In contrast, if a clot forms postmortem (after death), it tends to lack these distinct layers. Postmortem clots are often called postmortem clots or “postmortem clots without Lines of Zahn.” The absence of Lines of Zahn in a clot can be a forensic indicator that the clot formed after death.
explain the key differences between antemortem thrombi (thrombi formed before death) and postmortem clots (clots formed after death)
Antemortem Thrombus:
Adherent to Vessel Wall: Antemortem thrombi are often adherent to the vessel wall.
Color: They can be red in color.
Composition: Lines of Zahn are often present, indicating alternating layers of platelets and fibrin. These thrombi have a laminated appearance.
Postmortem Clot:
Not Adherent to Vessel Wall: Postmortem clots are not adherent to the vessel wall.
Color: They may have a gelatinous upper layer resembling chicken fat, with a fibrin network that includes red cells and leukocytes. This can give them a red appearance in certain areas.
Composition: Postmortem clots lack Lines of Zahn, and they are generally bland and non-laminated.
give an overview of some terms related to blood clotting disorders and platelet levels
Hypercoagulability and Thrombophilia:
Hypercoagulability: This refers to a state in which there is an increased tendency for blood clot formation. Another term used synonymously is thrombophilia.
Causes: Various factors can contribute to hypercoagulability, including trauma, major surgery, pregnancy, postpartum period, inherited thrombophilia, infection, inflammatory bowel disease (IBD), autoimmune conditions, estrogen therapy, inflammation, and dehydration.
Association with Venous Thrombosis: Hypercoagulable states are commonly associated with an increased risk of venous thrombosis (formation of blood clots in veins).
Thrombocytosis:
Thrombocytosis: This term is used to describe a higher than normal number of platelets in the blood.
Causes: Trauma, major surgery, pregnancy, and inflammatory conditions can contribute to thrombocytosis.
Platelet Levels:
Thrombocytopenia: Refers to low levels of platelets in the blood.
Thrombocytosis: Describes high levels of platelets with a known cause (secondary thrombocytosis).
Thrombocythemia: Indicates high levels of platelets with an unknown cause (primary or essential thrombocythemia).
explain various potential fates or outcomes of blood clots, particularly in the context of vascular events
Dissolved by Fibrinolysis:
Fibrinolysis is the process by which clots are broken down and dissolved. Plasmin, an enzyme, plays a key role in breaking down fibrin, the main component of blood clots. This natural process helps to prevent excessive clot formation and aids in the resolution of clots.
Propagation into a Larger Clot:
In some cases, a small clot may grow or propagate, incorporating additional platelets and fibrin. This can result in the formation of a larger clot. The ability of a clot to propagate depends on factors such as the balance between pro-coagulant and anticoagulant factors in the blood.
Recanalization into the Wall:
Recanalization refers to the process of reopening or creating a new channel within a blood vessel that has been previously obstructed by a clot. This can occur through the re-establishment of blood flow within the vessel wall, helping to restore the patency of the vessel lumen. Alternatively, the blood may find an alternate pathway to bypass the obstructed region.
Dislodged and Embolization:
A clot can dislodge from its original site and become an embolus. An embolus is a clot or other material that travels through the bloodstream and can lodge in a smaller vessel, leading to potential obstruction. This process is known as embolization and can result in complications depending on the location where the embolus lodges.
explain embolism and various types of emboli
Embolism Definition:
An embolism is a detached intravascular solid, liquid, or gaseous mass that is carried by the blood to another site within the vascular system, where it can cause obstruction.
Types of Emboli:
Detached Thrombus:
Accounting for the majority of cases (99%), a detached thrombus refers to a blood clot that has formed in one location (thrombosis) and becomes dislodged, traveling through the bloodstream to obstruct a blood vessel at a distant site.
Fat Embolism:
Fat embolism occurs when fat globules enter the bloodstream, often as a result of trauma, and can travel to and obstruct blood vessels in various organs.
Air Embolism:
Air embolism is caused by the entry of air into the bloodstream, which can happen during certain medical procedures or trauma, leading to the formation of air bubbles that can travel and block blood vessels.
Parasitic Embolism:
Parasitic embolism is a rare type involving the transportation of parasites through the bloodstream to distant sites.
Tumour Embolism:
Tumour embolism refers to the transport of tumor cells through the blood to other parts of the body, potentially leading to the formation of secondary tumors.
Amniotic Fluid Embolism:
Amniotic fluid embolism is a rare but serious complication in which amniotic fluid enters the maternal bloodstream, potentially causing obstruction in blood vessels.
